#include <iostream>

int main()
{
	double number = 0.0;
	int n = 0;
	
	double sum = 0.0;

	std::cout << "Enter number or -1 to quit:" << std::endl;

	while(number != -1)
	{
		std::cin >> number;

		if(number != -1)
		{
			sum += number;
			n++;
		}
	}

	if(sum != 0.0)
	{
		sum /= n;
		std::cout << "Mean: " << sum <<std::endl;
	}

	return 0;
}